Remote control school bell
Remote control school bell
Remote control school bell
Remote control school bell
Remote control school bell
Example video What you'll need:
- a wireless doorbell
- 1 x transistor (like bc547)
- 1 x relay
- 1 x 1K resistor

Tools:
- some solder
- a soldering iron
- ....

Step 1: How it works

Remote control school bell
Normal:
When you push the button
=> The remote sends a signal.
=> The doorbell receives the signal and makes a pin high in an IC on the PCB.
=> That pin TRIGGERS the sound controller.
=> The sound controller sends a signal to a speaker.
=> The speaker makes an annoying sound.

Hacked:
When you push the button:
=> The remote sends a signal.
=> The doorbell receives the signal and makes a pin high in an IC on the PCB.
=> That pin TRIGGERS our new circuit.
(the transistor lets a current flow so the relay can switch on).
=> The relay switches on and lets a current flow trough the school bell.
=> The school bell rings "tringggg!!!!!!!!!!!! ".
=> And you can leave the class :D


Step 2: How to find the trigger pin

Remote control school bell
Remote control school bell
Use the flowchart

Step 3: Making the circuit

Remote control school bell
Remote control school bell
Remote control school bell
V+ is connected to the positive lead on the battery-pack of the doorbell.
GND is connected to the negative lead on the battery-pack of the doorbell.
Trigger is connected to the triggering pin of the doorbell.

G5-8 = are normal battery's
R1 = 1KOhm
D1 = A normal diode like 1n4007 or 1n4004
K1 = NO relay 5V
T1 = A standard transistor like BC547

Step 4: Testing

Remote control school bell
Remote control school bell
When the school bell is not connected you can hear the relay switching when you push the button.
TEST 1 And when everything is connected the bell will start ringing when you push the button till you lose the button.
TEST 2
 
 

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